Final answer:
The valence shell of an atom is the outermost-occupied electron orbital energy level. It contains the electrons that are most likely to participate in chemical reactions and bonding with other atoms.
Step-by-step explanation:
The valence shell of an atom is the outermost-occupied electron orbital energy level. It is the shell that contains the electrons that are most likely to participate in chemical reactions and bonding with other atoms. Valence electrons are responsible for determining the chemical properties of an element.